Audio / Buying Guide

A Guide to Classic Studio Gear: Compressors

When I was trying to decide what outboard gear to cover first for this ongoing “Studio Classics” guide, I knew I wanted to start with classic compressors; the kind that have been heard on your favorite recordings and are considered “stock” studio gear. Sure, the importance of EQs cannot be overstated (and will surely be covered), but I have a particular fondness for compressors. Responsible for helping to control your dynamic range, whether it is just a touch or a flat-out squash, or helping to shape your tone, these compressors have defined the sound and feeling of countless classic recordings, and their footprint can be found in countless studios.

Arguably the most recognizable compressor of all time is the 1176LN Peak Limiter, commonly called the 1176. It was designed by legendary recording engineer Bill Putnam, and originally released by his company, UREI, in 1968. The 1176 was the first completely solid-state compressor to be released (meaning it required no tubes). The 1176 has been through more than a handful of revisions, but one of the most popular remains the revision D, which is still available from the company that sprang from UREI’s ashes, a little operation called Universal Audio.

Since its release, engineers have fallen in love with the 1176 on guitar, bass and, quite often, vocals. Noted for its incredibly fast attack (less than 20 milliseconds at its fastest), the 1176 is particularly at home on drums, and is the go-to compressor for many for the snare drum, and when stereo-linked, on room mics. One of the most famous features of the 1176 is its “all-in” feature (also known as British mode), where you can press down all the fixed ratio buttons to create a near infinite to zero ratio, perfect for annihilating drums.

While the original UREI versions remain quite sought after, the 1176 is one of the most cloned and copied compressor designs, and its fandom easily extends to software, making it pretty easy for you to get your hands on that sound. Thanks to it being one of the most emulated software plug-ins, a lot of engineers who get their start entirely in the box are comfortable with a hardware-version 1176 when they move onto pro studio work or a hybrid setup.


Warm Audio WA76 Limiting Amplifier
 

If the 1176 exemplifies the concept of a rough and rugged compressor that can grab and smash (though not limited to that function), then the LA-2A Leveling Amplifier is its elegant cousin. It was originally produced by the Teletronix company in the early 1960s, later bought out by UREI and, as such, is still made by hand at Universal Audio today. This incredibly popular (and pricey) single-channel compressor is used on a ton of different sources, such as bass or acoustic and electric guitars, but it shines on vocals like very little else can. It has gone on to inspire everything from plug-ins to guitar stompboxes.


Teletronix Leveling Amplifier Model LA - 2A
 

The LA-2A is what is known as an optical compressor. It features a transducer, which converts the incoming voltage of your audio signal into light, which, when coupled with a sensor, is responsible for gain reduction. This optical technology is responsible for a number of (what will ultimately be) sonic characteristics. First, it has a much slower attack in comparison to the 1176, and, once again unlike the 1176, the attack is not adjustable. This gives the LA-2A a fixed soft knee (gentle attack curve). Secondly, when converting the optical signal back into an electrical one, the transduction is highly non-linear, which results in very pleasing characteristics, which helps define the LA-2A’s “vibe.”

Couple all of that with a tube-driven output stage, it is no wonder the LA2A has been heard on thousands of recordings since its release. The compressor itself has very simple controls, a single knob for peak reduction and a second knob for gain. It is not uncommon for engineers and mixers to chain the LA-2A with a second compressor, letting a vocal track hit the LA-2A for its character and gentle compression, while using a second compressor to limit peaks more aggressively.  

If there is one subject that almost every mix engineer has pretty passionate opinions on, it is what stereo bus compressor is the best. There is no shortage of great stereo compressors that have served duty on the mix bus of amazing albums, and almost every one of those compressors is someone’s favorite. While a simple trip to your favorite recording forum will, no doubt, bring you thread upon thread on the topic, there is one thing no one can really dispute: the trend of mix-bus compression started with the SSL. As the popularity of mixing on SSL G-series consoles rose in the 1980s, more and more mix engineers used and fell in love with the integrated bus compressor on the popular mixing desk. Eventually, SSL began to manufacture the compressor as a stand-alone rack unit, for their X-Rack system, and as a 500 series module.


Solid State Logic X-Rack Stereo Bus Compressor Module
 

It has become known as the glue that holds your mix together, and is one of the most important pieces of equipment in modern recording and mixing. Typically used in a gentle fashion (with only a few dB of reduction), the SSL is renowned for its auto-release function, which helps avoid over-pumping your mix. It remains one of the most cloned and emulated pieces of equipment, and, while there is no shortage of great stereo bus compressors available, the SSL (and its clones) remains the most popular.

A definitive modern classic, Manley Lab’s Vari Mu is a stereo compressor/limiter with dual mono capabilities, and is the baby on this list, being released in 1994. While it is not uncommon to see it used for tracking, this beloved piece of gear is most well known for duties on the stereo bus or in mastering. Manley’s motto is “Tubes Rule!” and that philosophy is evident in the Vari Mu. It uses a 5670 dual triode tube for its peak reduction, which is constantly being re-biased by a tube-driven rectifier side chain, resulting in smooth gain changes. Confused? Don’t worry; like most gear, understanding its operating principles is not required to use it.


Manley Stereo Variable MU Limiter Compressor
 

The Vari Mu has both compression and limit functions. Its compression ratio is fixed at a gentle 1.5:1, making it a favorite for subtle compression with gorgeous color. When you flip the switch to limit, it starts off with a 4:1 ratio that increases as gain reduction is driven by adjusting threshold, attack, and release. It is capable of up to 20:1 limiting when you really drive it. The Vari Mu is no doubt a color piece, and can impart a unique sonic quality simply by running your mix through it without any gain reduction. While the Vari Mu has been cloned by quite a few companies, most of them have as hefty a price tag as the original.

There is a world of dynamic processing available, and every engineer seemingly has a personal favorite for almost every given application, whether hardware or software. However, the entries on this list have a special place in studios around the world and have been heard on countless hits and albums. What’s your favorite compressor?